Abstract
The author, like many others interested in the application of instruments to process control, has felt the need of an analytical approach to the problem, particularly in the case of temperature control, which includes the more common as well as the more difficult processing problems. He suggests a classification of controllers as on-and-off, floating, proportional narrow-band, proportional wideband, and proportional reset types. He then proposes a classification which considers the controlled process equipment as types of heat exchangers. Starting with counter-current exchangers, he considers the control requirements of the various simple and compound types, and identifies the design factors favoring controllability as minimum transportation and transfer lags, minimum temperature difference, and maximum ratio of demand-side to supply-side thermal capacity. Next he considers a few practical examples. Finally, he discusses the pitfalls of unsystematic behavior of the control system.
The author seeks critical comment, and urges cooperative effort so that some theory of control application soon may be developed on a quantitative basis.
